In various power conversion systems, such as AC/DC and DC/DC converters, field effect transistors or FETs (MOSFET transistors, for instance) driven by control logic can replace rectifier diodes.
This technique, oftentimes referred to as synchronous rectification (SR), is found to improve converter efficiency. Resorting to SR facilitates reducing conduction losses insofar as the (rectified) output current flows through the MOSFET channel instead of the rectification diode, with power losses correspondingly reduced.
Such a power converter continues to operate also if a synchronous rectification FET is not driven. This is because rectification is still provided by an internal body diode (essentially body-to-drain, with body-to-source being irrelevant insofar as this is shorted out by an internal body-to-source connection).
The body diode (which is intrinsic to most FET types) may however exhibit poor performance: properly driving a (MOS)FET, when the body diode is forward biased, may increase system efficiency by about 3%-4%.